This invention relates to dental air syringes, and more particularly to a replaceable filter cartridge which is releasably insertable into a compressed air supply line adjacent to a dental air syringe, both to remove residual fluids and/or particles from the air, and to provide visible means for determining when the cartridge need be replaced.
Dentists have long employed compressed air for drying tooth surfaces during the execution of a variety of dental procedures. Typically a fine jet of compressed air is directed into the mouth of a patient through the nozzle portion of a small, hand-held dental syringe. At its end remote from its nozzle the syringe usually is connected to a compressed air supply by a flexible tube, which permits the dentist or his assistant to manipulate the syringe manually.
One of the major problems of dental air syringe systems of the type currently employed is the need for removing moisture and oil from the air before it is delivered to the patient's mouth. For example, current research has developed a variety of dental materials that rely upon a critical "bonding" of the material to tooth dentin or enamel. During procedures utilizing such materials the dentin or enamel first must be chemically treated to produce a clean, reactive surface, after which the surface is washed with water and air dryed before applying to the surface the particular material which is to be used for covering or rebuilding the tooth surface. It is essential that the air, which is used for drying, be completely free from moisture and oil to prevent contamination of the reactive surface. If water or oil is present in even the smallest amount, it will prevent proper bonding between the treated surface and the material which is being applied to the tooth dentin or enamel.
Heretofore it has been customary to use rather sophisticated compressed air dehydration systems for supplying dry air to dental syringes of the type described above. U.S. Pat. No. 3,279,151 for example, discloses a system in which compressed air passes through a chamber containing a desiccant which is designed to remove moisture from the air before it reaches the associated instrument. The system is adapted periodically to reverse the flow of air through the desiccant chamber, while at the same time heating the chamber to vaporize the moisture in the desiccant The moisture is then exhausted by the reversed air flow to atmosphere, thus restoring the desiccant so that it can once again be utilized for absorbing air.
The problem with this type of system is that, while it removes most of the moisture from the air, nevertheless residual amounts of moisture do in fact remain in the air after it leaves the desiccant chamber on its way to the dental syringe. In fact moisture laden air bypasses the desiccant chamber for 30 minutes during the heating cycle when the apparatus is first turned on. Moreover, the presence of the residual moisture and/or oil, in the air remains unknown to the dentist, who assumes the air to be dry, and therefore is unaware that moisture in the air may in fact have contaminated the reactive surface of the dentin or enamel.
U.S Pat. No. 4,487,618 discloses a rather sophisticated, heatless dehydration system using an in-line trap for removing water and/or oil vapor from a compressed air line. Although this system suggests using removable filter cartridges, the apparatus appears to have been designed for heavy machinery, and the patent was not at all concerned with the complete removal of moisture and oils for purposes of dental treatment.
In any case, these heatless or heat cycled type desiccant apparatus need to have the desiccant replaced periodically, but there is no way for the average dentist to know when such replacement is necessary. More importantly, since most such systems are well out of view of the dentist, the dentist or other operator has no way of knowing at any given instant whether or not the dehydrating system is properly functioning, and therefore may be unaware that a treated surface has become contaminated because of a failure in the filtering apparatus.
Furthermore, depending on the type of dental procedure employed it may be desirable, such as for example if oral surgery is involved, to remove even the smallest of particulate matter from the compressed air before applying it to the site of the wound or incision.
It is an object of this invention, therefore, to provide for dental air syringes of the type described a novel filter cartridge which is disposed to be releasably mounted in the compressed air supply line of the syringe to remove residual moisture and/or oil from the air.
It is another object of this invention to provide an improved cartridge of the type described which is adapted to be positioned in the compressed air supply line of a syringe in such a manner that one or more filter elements in the cartridge are readily observable by the dentist, and are designed to undergo a change in color when saturated or clogged, thereby to provide a visible indication of when the elements need be replaced.
Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims, particularly when read in conjunction with the accompanying drawings.